1. Field of the Invention
The present invention relates to a zoom lens and an image capture apparatus having a shake correcting function, i.e., a function of correcting blurry images resulting from camera vibration. Particularly, the invention relates to a zoom lens and an image capture apparatus which are suitable for an imaging optical system of digital input/output equipment such as digital still cameras and digital video cameras, which also have a high zooming ratio and the shake correcting function, and which are particularly superior in size and thickness reductions, as well as to a method for controlling the zoom lens.
2. Description of the Related Art
In recent years, image capture apparatuses using a solid-state imager device, such as digital still cameras, have become increasingly popular, demanding still higher image quality. In, e.g., digital still cameras using an imager device having a large number of pixels, in particular, an imaging lens, particularly a zoom lens, superior in image forming performance ready for the solid-state imager device having a large number of pixels is called for.
Particularly of late, there is a strong demand for the shake correcting function for preventing blurry images caused by camera shake during imaging. In addition, miniaturization is strongly called for, with a special demand for a zoom lens small in a depth direction, i.e., in an entrance optical axis direction.
For example, a zoom lens disclosed in Japanese Unexamined Patent Application Publication No. 01-189621 has a plurality of lens groups, and corrects a blur caused when the zoom lens vibrates, by shifting a first lens group positioned closest to an object side, in any direction perpendicular to an optical axis.
Furthermore, a zoom lens disclosed in Japanese Unexamined Patent Application Publication No. 11-282038 has a plurality of lens groups, and corrects a blur caused when the zoom lens vibrates, by shifting a movable lens group moving in an optical axis direction during zooming or focusing, in either direction perpendicular to the optical axis.
Furthermore, a zoom lens disclosed in Japanese Unexamined Patent Application Publication No. 2001-124992 or 2001-356270 has a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having negative refractive power, and a fifth lens group having positive refractive power arranged in order of mention from the object side, performs zooming by moving at least the second lens group and the fourth lens group on the optical axis, and corrects a blur caused when the zoom lens vibrates by moving the whole third lens group positioned near an aperture stop, in either direction perpendicular to the optical axis.
Furthermore, a zoom lens disclosed in Japanese Unexamined Patent Application Publication No. 01-191113 has a plurality of lens groups, and corrects a blur caused when the zoom lens vibrates, by shifting a final lens group positioned closest to an image side, in either direction perpendicular to the optical axis.
Furthermore, a zoom lens disclosed in Japanese Unexamined Patent Application Publication No. 2006-71993 has a plurality of lens groups, in which a final lens group positioned closest to the image side and having negative refractive power is fixed in both optical axis directions during zooming and has a front group having negative power and a rear group having positive power. By configuring the rear group having positive power or a part thereof (“blur correcting lens group”) to be movable in either direction orthogonal to the optical axis, the zoom lens corrects a blur caused when it vibrates, by moving the blur correcting lens group in either direction perpendicular to the optical axis.
Meanwhile, in some other zoom lenses, an optical system is folded by inserting a prism between lenses, thereby realizing a size reduction in the entrance optical axis direction, and lenses are cut with respect to a short-side direction of the imager device, thereby realizing a thickness reduction in the structure of a lens barrel.